BELL RINGER 1/7/16 • What special characteristic/feature would you only find in sedimentary rocks? IGNEOUS ROCKS • Igneous rocks form as a result of cooling and solidifying of rock material that was once molten. • Lava: Molten rock material on earth’s surface • Magma: Molten rock material inside of earth • Igneous rocks are classified based on where they formed • Intrusive (Inside of Earth) – underground from magma • Examples: Granite Peridotite Pegmatite Gabbro • Extrusive (Exited Earth and is now on the surface) – at the surface from lava • Examples: Basalt Rhyolite Pumice Scoria FORMATION OF IGNEOUS ROCKS • Solidification: Changing from a liquid to a solid • Crystallization: Liquid to solid that causes crystals to form COOLING RATE 1. Slow – magma cools slowly underground. This give crystals a chance to grow, resulting in larger crystals. COOLING RATE 2. Fast – lava cools quickly at the surface because it is exposed to air and water****. This doesn’t allow crystals to grow, resulting in small crystals. • **If cooling rate is really fast, no crystals grow, resulting in a glassy texture. RELATIONSHIP BETWEEN COOLING RATE AND CRYSTAL SIZE C r y s t a l s i z e Cooling Rate IDENTIFYING IGNEOUS ROCKS 1. Determine Texture • Coarse- Minerals visible to the naked eye • Examples: Granite, Pegmatite, Gabbro • Fine- Need magnification to see minerals • Examples: Basalt, Rhyolite, Andesite IDENTIFYING IGNEOUS ROCKS 2. Use grain size to determine texture IDENTIFYING IGNEOUS ROCKS 3. Check color and density for composition IDENTIFYING IGNEOUS ROCKS 4. Use chart for mineral composition • http://www.ck12.org/book/CK-12-Earth-ScienceConcepts-For-Middle-School/section/3.8/ • Lava Flow GoPro • Lava entering the ocean • Smart or not so smart?